Application of the simulation models THESEUS and HYDRUS-1D ...€¦ · Application of the simulation models THESEUS and HYDRUS-1D at different european forested test sites Martin

Modelling-Workshop Freising 27th-29th April, 2010

Application of the simulation models THESEUS and

HYDRUS-1D at different european forested test

sites

Martin Wegehenkel

Institute of Landscape Systems Analysis

ZALF Müncheberg


• Outline:

• Application of the models THESEUS (Wegehenkel, 2005) and HYDRUS-1D (Simunek et al., 2008) at 9 forested experimental test sites

• Test and comparison of both models

• Analysis of simulation precision and data quality

• Presentation of some selected results: Celerina, Solling Spruce and Solling Beech


Hydrus-1D (Simunek et al. 2008) THESEUS (Wegehenkel 2005)

Time scale Minutes – Years Days – Years

Profile discretization 1 cm layer = 90-280 layers depending on soil profile depth

10 cm layer = 9 -20 layers depending on soil profile depth

Time Step Seconds - daily Minutes-daily

Met. Data Time series of net precipitation, evaporation, transpiration calculated by THESEUS and LAI from the data providers

Time series of precipitation, temperature, global radiation, air humidity and wind speed

Vegetation - Semiempirical forest model using external time series of LAI and rooting depth as driver variables

Evapotranspiration - Penman-Monteith equation based on algorithms obtained from the model FOREST_BGC (Running et al. 1991)

Interception - Single linear storage using LAI

Ψ(θ) and K(Ψ) Van Genuchten (1980) Van Genuchten (1980)

Soil water fluxes Richards-Equation using numerical solution

Simple Richards equation using the model SAWAH (Ten Berge et al. 1998)

Inverse modelling Hydraulic parameters using time series of measured pressure heads, soil water contents and fluxes

No

Heat transport Yes No

Dual porosity Yes No

Solute transport Yes No

Graphical uses interface Yes No

Comparison of the actual model set up for Hydrus-1D and THESEUS


Forest-Model

1. Calculation of potential transpiration Tpot in mm d-1 (RUNNING und COUGHLAN 1988, RUNNING und

GOWER 1991)

10001

sec LAIT

ar

cr

ar

vpd

pc

crad

Tpot

= slope of the function saturation vapour pressure versus air temperature (mbar K-1), radc = Net

radiation (W m-2), cp = specific heat of air at constant pressure (J kg-1 K-1), = air density (kg m-3), vpd

= vapour pressure deficit (mbar), ra = aerodynamic resistance (s m-1) = Psychrometerkonstante, rc =

canopy resistance (s m-1), Tsec = day length (sec), = latent heat (J kg-1), LAI = Leaf area index (m2 m-2)

2. Interception using specific interception capacity of the forest stand IC (mm d-1): sec,

TradICLAICICMinInt c

ic

CIC = specific interception coefficient (LAI-1 d-1).

3. Evaporation PE in mm d-1

IntTrad

PE c sec

Transpirationmodel THESEUS


Modelling procedures:

• No correction of precipitation inputs

• The Van Genuchten parameters θs, θr, α and n were estimated by the

program SHYPFIT (Durner 2005) using the provided soil water contents

at pF4.2 (=WP), pF2.0 (=FC) and pF0.0 (=total porosity)

• θs, θr, α and n for organic layers obtained from literature

• Initial moisture conditions obtained from the corresponding data set

• Uncalibrated (= no parameter optimization) application of THESEUS at

the test sites Celerina, Solling Beech and Solling Spruce

• Using LAI, rooting depth and phenogical data from the corresponding

data sets

• THESEUS provides time series of net precipitation, evaporation,

transpiration, LAI and rooting depth as input and upper boundary

condition for the application of HYDRUS-1D

• Inverse modelling of hydraulic parameters with Hydrus-1D using time

series of measured pressure heads at the Solling Spruce test site

• Using optimized hydraulic parameter set in the application of Hydrus-1D

and THESEUS at the Solling spruce test site


Comparison of simulated (by THESEUS) and measured daily throughfall,

Solling Spruce


Daily rates of precipitation (Prc in mm d-1), measured and simulated pressure

heads in 10 cm, 20 cm, and 40 cm depth (Prh10-Prh40 in hPa), Solling Spruce



heads in 100 and 180 cm depth (Prh100-Prh180 in hPa), Solling Spruce


Daily rates of precipitation (Prc in mm d-1), measured and simulated soil water

contents in 2 cm depth (Swc2 in Vol%), Solling Spruce


Comparison of simulated and measured soil water contents,

Solling Spruce, 2cm depth

Hydrus-1D THESEUS


Comparison of simulated (byTHESEUS) and measured daily

throughfall, Celerina (left) and Solling beech (right)



heads in 15 cm, 30 cm, 50 cm and 80 cm depth (Prh15-Prh80 in hPa), Celerina



heads in 10 cm, 20 cm and 40 cm depth (Prh10-Prh40 in hPa), Solling Beech



heads in 100 cm and 180 cm depth (Prh100-Prh180 in hPa), Solling Beech


• Preliminary conclusions:

• Van Genuchten Parameter estimation with only three points – uncertainty in hydraulic functions.

• Van Genuchten Parameters for organic layers difficult to identify

• THESEUS model had problems with stagnant water and saturated conditions at the lower soil profile boundary – due to the simple procedure to solve the RICHARD‘s equation (see results for Solling beech site).

• Inverse modelling procedures depend on the quality of the data used for the objective function and reliable estimates of the range of the parameters.

• In the actual state, overall simulation quality of both models using e.g. the comparison of simulated with measured soil water contents is bad (see 2cm depth at Solling Spruce site).

• Check of model calculations and measured data.


Thank you for your attention !

A special thank to the organizers of the workshop

and the data providers as well !

Documents

Application of the simulation models THESEUS and HYDRUS-1D ...€¦ · Application of the simulation models THESEUS and HYDRUS-1D at different european forested test sites Martin